In numerous medical and surgical techniques, there exists a need for inserting stents, implantable tubular prostheses, either temporarily or permanently, into various body ducts which are difficult to access. The stents may be used in cardiovascular medicine as an adjunct to percutaneous transcatheter angioplasty for treating ischemic heart disease and peripheral vascular disease or may be used in other medical or surgical applications to maintain the patency of passages. Transluminal stent implantation requires that the prosthesis diameter be smaller than the access passage during implantation. Following implantation, the stent would ideally restore the inside duct diameter to that of adjacent lumens in order to minimize turbulent flow.
The art has been replete with tubular prosthesis for generating a limited radial expansive force during surgical procedures.
U.S. Pat. No. 3,868,956 to Alfidi et al., Mar. 4, 1975, discloses an expandable device including a helical coil made of a nickel-titanium alloy with memory properties. Once placed in a desired position, the device is heated causing it to resume its expanded configuration. However, it is generally understood that the application of such heat may produce thermal tissue injury and inadvertently coagulate blood. Moreover, this device produces a limited expansive force and the small surface area of contact with the body duct leads to high localized stresses which may also damage tissue.
U.S. Pat. No. 4,503,569 to Dotter, Mar. 12, 1985, discloses a transluminally placed endovascular graft prosthesis including a helically wound coil having a generally tubular shape. This device is similar to that used by Alfidi et al. in that it relies on the shape memory of a metal alloy. Dotter seeks to reduce the risk of thermal tissue injury and blood coagulation by employing a lower restorative transition temperature material. However, this device also generates a limited radial expansive force which is also exerted over a generally small area resulting in high local stresses that lead to tissue injury.
U.S. Pat. No. 4,183,102 to Guiset, Jan. 15, 1980, discloses a prosthetic device for introduction into a lumen and for lining an interior wall portion of the lumen. This device includes a hollow toroidal inflatable sleeve which is expanded with pressurized fluid and can be placed in series to form an implantable sleeve. The sleeve generally has poor inside/outside diameter ratios which reduces fluid flow and causes turbulent flow in some instances. Moreover, this device is understood to be limited to short term applications.
U.S. Pat. No. 4,592,341 to Omagari et al., June 3, 1986, discloses methods and apparatus for guiding a prosthesis utilizing a flexible sheath in combination with a guide member. The prosthesis is not expandable and must be forcibly driven into the stricture. The rigid design may limit the usefulness of the device and has the capability of producing soft tissue trauma during insertion.
U.S. Pat. No. 4,655,771 to Wallsten, Apr. 7, 1987, discloses an expandable tubular prosthesis made of multiple helical coils wound in a braided configuration which are expanded radially by axially contracting the tube. This device, however, requires the prosthesis to be firmly fixed in position to remain expanded and generates only a limited radial expansive force.
U.S. Pat. No. 4,732,152 to Wallsten et al., Mar. 22, 1988, discloses an applicator used to place the expandable tubular prosthetic device described in the Wallsten '771 patent.
U.S. Pat. No. 4,665,918 to Garza et al., May 19, 1987, discloses a tubular prosthesis comprising a precompressed spring-like device wrapped around an applicator and held in a contracted state by a sheath. After proper device positioning in a blood vessel, the sheath is withdrawn and the precompressed spring radially expands by spring tension. However, this spring tension limits the maximum prosthetic diameter and the expansive force applied to the vessel walls.
While in the main, these devices are illustrative of the state of the art in transluminally expandable prostheses, there remains a need for improved prosthetic devices intended to be introduced, either temporarily or permanently, into the interior of longitudinal body passages and to be fixed in position to form a patent longitudinal channel. There also remains a need for implantable tubular prostheses which can avoid the need for surgical intervention by providing significant wall support and improved luminal patency while avoiding the many drawbacks of known radially expansive tubular prostheses.